In general, there is proposed a hollow injection molded body such as a side turn lamp that is formed by molding (primary injection molding) a first member and a second member using a first mold and a second mold, sliding the molds until the first and second members abut each other, and performing secondary injection molding to integrate the both members (refer to Patent Document 1).
However, there are problems in that, since secondary injection is performed for integration after primary injection, production efficiency is low and costs increase.
Here, a technique in which a first mold is rotation type, mold surfaces of male, male, and female molds are formed on the first mold, and mold surfaces of male, female, and female molds are formed on a second mold, the first mold is rotated 120 degrees, and primary injection for molding first and second members and secondary injection for integrating the first and second members are repeated is known (refer to Patent Literature 2).